[secant0give]

After enjoying Pylon racing for a little while I thought I might give large scale racing a go. There are, I think only 3 or 4 events a year The models are not specifically racing models, and for most of the classes they are more like scale models of racers rather than purpose built racers. Most of the classes really don't go faster than a q-500 but because of their size they look quite slow and are in some ways easier to fly.

The racing is quite different too, there is a flying start which works much like the start of a sailing boat race. All the planes are in the air milling around, there is a count down and the idea in to cross the start line as soon as possible after the zero count, do ten laps and then prepare to land. The course is more than 500m per lap so it's bigger than the FAI pylon course but unlike FAI style pylon the pilots stand outside the course and fly around the pylons from there. There are the usual callers and judges.

The classes are quite interesting and not very tightly defined with the entry level class being called Red Bull, the rules say the airframe has to one that can take a 120 size engine and be a scale model of any plane that's competed in a national or international aerobatic competition or the red bull air race. There's a bit more to the rules than that but I'm not going to type them all up, here's a link it explains the other classes as well.

http://www.rcmn.com.au/Aust_F1_LSRCA-201...202014.pdf

I've never been to one of these race days but I imagine it would be quite spectacular seeing some of the bigger classes race!!

The red bull class has so far this year been dominated by the seagull MSXR air frame with an OS 120 special, power plant, Some people might remember the one Wayne had set up for electric power. It would have had very similar performance to IC powered machines flown in this class.

Any way I'd better mention the subject of this thread, I was getting there ...............Ah yes the Harmon Rocket. At the present time you can't for love, money or even a kidney get a Seagull MSXR air frame. So I ordered the next best thing a Seagull Edge 540. These are more a sports aerobatic models than 3D machines, they are a little more heavily built and have smaller control surfaces than you find on a 3D plane. They designed to fly pattern style aerobatics. I managed to get the last one in captivity and a good deal on shipping from the UK but to my great dismay the courier managed to drop a pallet on it and destroyed the airframe completely even before the box was opened.
So after a little bit of soul searching and a good deal of web searching I managed to find something that would meet the class rules and was available and one I could get my hands on in a reasonable time frame. Here it is, you guessed it, the Harmon Rocket. You'll be forgiven for thinking Crikey what is that?? I've never heard of it?? Well neither had I that's probably why it took me a bit of searching to find it

Here's a link http://blackhorsemodel.com.vn/?product=harmon-rocket

It's a scale model of kit plane that is an upgrade of an RV4. The RV4 is a sports aerobatic home built 2 seater, It's been used in heaps of full sized aerobatic competitions in Intermediate and sportsman classes so it fits the rules. YAY !!

It arrived today and I must say it is a really nice kit It's beautifully made, the finish and fit of parts is EXCELLENT!! It's a very nice scale model and it's remarkably light but robustly built at he same time. It's not a cheap kit by any means but I think the value is plainly visible as soon as you open the box. Everything is done nicely the hardware is great, the hinges are superb and it looks like it will go together quickly, even the wheels are light weight. I'm super impressed and would defiantly by another Black Horse ARF !!

Here's the fuse
   

And the pilot
   

[Claudius]

Looks great Jason - as much as I was looking forward to seeing the 540 in action (what a shame!), I can't wait to seeing you give the guys a hurry up with this machine.

[Steven]

I checked the link back, that will be a lovely little plane. Watching how this happens.

I don't want to threadjack, but I've collected a couple of larger fasty pasties over the last year. More for the love of building, but they do have an appeal. Might get the chance to race you one day lol.

[secant0give]

Very cool Steven!!
You can certainly race the Pogo in The EF1 class, That class is getting quite a decent following now you should come out to Pitt Town next weekend and have a look !!

[Steven]

I'll have miss this one, Jason, I'll be away again. The Cassutt is ready to go when ever I'm feeling game, but the Pogo needs some work. I set it up to run the milder Power 15 sports configuration, but my 15 has a mysteriously bent shaft now... and one of the HS225MG's is faulty. No hope of returning that to place of purchase :/

I do have a spare 60A ESC and the 1250kv Power 25 rolling around, but not sure if I'm ready for that yet.

[secant0give]

All in good time Steve, probably better to put the bigger power plant in it and use an 8X4 prop instead of the 8X8 that would tame down the top speed and reduce the torque reaction and you'd till have the grunt to accelerate when you need to.

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I got all the servos mounted in the wings and the radio programmed and the linkages sorted fort he flaps, just got to do the aileron linkages and the wings are finished

[secant0give]

I did some more work on it this evening
All the servos are in except the throttle
This Kit goes together very nicely the fit of all the parts is brilliant !!

I've used HXT 12 servos for everything they are light and have truckloads of power !!

Here's a couple of pics

   

   

[secant0give]

In this class competitors can modify their engines and run what ever fuel they choose.

Never in the history of areomodling have engines been so cheap this is an ASP 120 from HK for under $130 and they arn't too badly made inside especially once you get rid of the horrible bearing that they come with out of the box.

So we start with a bit of measuring up

Checking to see what the induction, intake, boost and exhaust timing is

   

replace the Chinese bearing with Japanese ones

   

Adjust the induction valve open duration to make it close a little later with out alter the opening timing.

   


After adjustment, basically surface grind the slot down a little more of one side

   

There's nothing like a bit of masking tape to protect precision surfaces from accidental damage while dremmeling away on important parts.

You can see I've rounded the edge of one of the rotary induction valves opening to improve the flow of fuel air mix into the engine.

   

And in the last photo there's the standard crank on the left and the one I've rounded out the opening in the end of the other one. Again this is to help to help the fuel air mix flow through the engine. When the engine is assembled and running, the connecting rod partly obscures this hole in the back of the crank during some of the time the fuel air mix being inducted. So having the rounded edge not only decrease the turbulence caused by the sharp edge it also increases the size of the opening for that part of the induction cycle

[secant0give]

A little more improvement this time to the connecting rods. These things get to flail around pretty hard down there in the crank case, I didn't want to take too much meat off them but I did want to make them a little less draggy so I've rounded then off a bit to make them a little more aerodynamic. Pics show the original rod and one I've done some work on

   

   

[secant0give]

I did a bit more work on the engine over the last week.

There's a bit of an issue with the OS engines getting hot in the MXSR airframes. I'm not sure how much this has to do with the design of the cowl or how badly the ASP engine would suffer temperature wise in the Harmon Rocket airframe. However I'm not going to take any chances as I'm asking the poor ASP to put out a bunch more herb than one of the OS 120 specials, hopefully it will comply. If it does it will certainly generate more heat and that will need to be dissipated.

I was rather unhappy with the shape of the original combustion chamber in the ASP, It didn't take much to see that it wasn't going to cut the mustard as far as my idea of performance goes. So I was resigned to making a new head for it. The initial thought was to make a button and machine the underside of the original head flat and re-use it as both, the retaining clamp for the button and the heat-sink. There are a few engines made like this. I was thinking this might not be the best solution because heat may not be conduct away as well via a clamped on heat-sink compared to a head manufactured from a single piece of metal.

It was Micky T who provided the inspiration for the totally new head because he brought a thunder tiger Heli engine along to the last indoor flying session and one look at the way the head was set up on that set the gears in motion for designing a 120 size version for the ASP.

Here's some photo's
Roughing out, the new head begins to take shape
   

Putting the narrow deep groves in between the fins

   

The combustion chamber is carved out to the carefully calculated dimensions

   

bolt holes are drilled in the right place

   

Glow plug hole is tapped and a bit of an extra air slot milled in on top

   

It all seems to fit OK and it definitely has a lot more cooling area than the original and a much better chamber as well !!............Hopefully

   

Now to mod the liner a bit (the one on the right is the original) The one on the left has the exhaust duration increased a little bit

   

And a quick test fit to find that there's no way the standard muffler will fit inside the cowl I'll need a bit of jiggery pokery in that department as well

   

[secant0give]

Well the engine runs and runs pretty well
It's doing a solid 10,000 rpm even with 25% oil in the fuel

I'm hoping it will pick up still more with a leaner meaner 18% oil

Here's the engine mounted to it's stand for running in.

surprisingly this is the easiest engine to start that I've ever owned
All you have to do for it to fire up is prime it attach the glow driver and grab the spinner and flick it backwards and it just roars to life every time...........Just magic !!

   

[secant0give]

Well after quiet a while back to this project
Hopefully its going to be ready to race in Canbera in the midfle of the month

Here's some pics of the frantic effort recently re-undertaken

   

This is the angle adapter to change the muffler position so i dont have a great big draggy hole in the cowel

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[secant0give]

The cowel fits with the muffler on Yay!

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Tank and throttle servo are in plumbing is done

[symowallo]

Ah! That's why we haven't seen El Presidente at the field for a while!

[samste]

looking Good

[secant0give]

Symo, Life has been busy, busy at home, busy at work and busy putting this machine together so It can be test flown before the weekend. I'm starting to look at ordering a bulk quantity of red bull to fuel the midnight oil so I can finish it all

Thanks samste, it's getting there. Black horse certainly make a very nice model!! I'd say even nicer than sebart. It's very very light and very strong. I'm hoping that it will be fast in a straight line too because it's going to zip around the corners that's for sure. If it is a reasonably quick airframe and the engine holds together and nothing bad happens I might have a chance at snapping at the heals of Tony J and Jag. If I can even rattle their cages a bit I'll stoked !! It's not like the FAI pylon classes tho' its flown from outside the course and I don't have a spare plane so I've got to be conservative and consistent and the plane has to be reliable. I'm hoping my cheap ASP engine will hang in there. It's a $150 engine that I've souped up and everyone else in this class is flying really nice $500 engines build for racing straight out of the box. One thing for certain is it will be great fun regardless of the outcome!!

[symowallo]

Ah. It looks awesome though Jason. I'm sure it's worth the effort.

[secant0give]

I guess I didn't finish off with a report on how this machine flies so here it is.

The Harmon Rocket was test flown 10 minuets before the start of racing back last year at the first Large scale race event I ever attended. The event was held at Canberra's NAAS field and what a superb weekend it was!!

It flew brilliantly It took off and buzzed around the sky like a dream. It handled superbly and was very friendly to fly with the rates I had initially set up. I haven't changed anything as far as rates and expo go. The rates are set quite low which is what you need for racing and expo is around 25% on all surfaces except rudder which uses 40. It flies like a trainer the only difference being that it's a little fast.

Because it's rather large it doesn't seem that fast in the air, however it does take up a fair bit of sky. It would make an absolutely brilliant sports model or second plane, Its that easy to fly. If it had a lower pitched propeller and if the engine would idle at a lower RPM it would be a very relaxed Sunday flier. With the steep pitched prop and fast Idling engine it's producing a little too much thrust to land so the engine must often be shut down on approach to allow it to slow up enough to get on the ground with out running out of strip.

I have flown it in three competitions now and thoroughly enjoy flying it. It is fitted with flaps and I have all them connected up and wired in but have never felt the need to use them. It's a really nice, strong and lightly built plane. Hats off the Black Horse models for doing such a nice job of making it. The only thing I added was some incidence pins to align the wings a little more positively because it was only relying on the spar and a couple of nylon screws which would slowly work loose due to the vibration of the IC engine.

[Spook]

Awesome, It looks great in your above pictures. Love to see it in action and I'll keep and eye out for your next event that is close enough to travel to

[secant0give]

   

Heres a picture of it fueled up and ready to race at Bendigo